67,280,421,310,721
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Number
$67,280,421,310,721$ is:
- The $n$th prime, where $n$ remains to be determined
- One of the two prime factors of the $6$th Fermat number $2^{\paren {2^6} } + 1$, the other being $274 \, 177$:
- $67 \, 280 \, 421 \, 310 \, 721 = 262 \, 814 \, 145 \, 745 \times 2^8 + 1 = 5 \times 47 \times 373 \times 2998279 \times 2^8 + 1$
- The largest prime to have been identified as such without the use of a computer. This was done by Fortuné Landry subsequent to his factorisation of $F_6$ in $1880$.
Also see
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $257$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $257$